Figure 1.

Equilibrium properties of ACTR in Urea. (a) Fluctuations in R_g over time at selected denaturant concentrations, concentration as labeled in (b). (b) Time correlation functions for R_g. (c) Dependence of mean R_g from simulations (blue solid line, filled circles), Guinier fit of SAXS intensity with q < 0.04 Å⁻¹ from explicit solvent calculation (black dash line, up triangles) and from implicit solvent calculation (black dotted line, down triangles). Red symbols show the data from large box simulations (see Table S1). (d) the dependence of the R_g included between residues i and j on the sequence separation |i − j|. (e) Dependence of root mean square intramolecular distances on denaturant concentration. Red symbols show data from large box simulations (see Table S1). (f) Dependence of root-mean-square distance between i and j on |i − j|. Scaling exponents were calculated by fitting a power law to the dependence on sequence separation |i − j| of either the root mean square distance between i and j in (f) or the R_g of the chain included between residues i and j. Solid lines show fits to ${<R_{\mathit{\text{ij}}}^2>}^{1/2}=\sqrt{2l_{p}b}{N}^{\nu }$ and ${<R_{g,\mathit{\text{ij}}}^2>}^{1/2}\approx \sqrt{\frac{2l_{p}b}{(2\nu +1)(2\nu +2)}}{N}^{\nu }$, in which l_p=0.4 nm and b = 0.38 nm³⁵ (the expression for R_g is an approximation which assumes Flory scaling to hold for all i,j pairs, although it is only strictly valid for sufficiently large |i − j|). Simulation error bars are obtained from block averages, as described in the SI text, and refer to the standard error of the mean.